This invention relates generally to vehicle suspension systems and more particularly to a multi-stage torsion axle, particularly for use with trailers.
In many instances, such as for boat trailers, horse trailers, utility trailers, both open and enclosed, and recreational trailers, the suspension system is designed to give an acceptable ride when the trailer is substantially loaded, but provide a poor and uncomfortably stiff ride when the trailer is very lightly loaded or has no load.
The foregoing illustrates limitations known to exist in present suspension systems Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.
In one aspect of the present invention, this is accomplished by providing a multi-stage torsion axle comprising: a first stage shaft; an elastomeric first stage bushing about the first stage shaft; a second stage shaft about the first stage bushing; an elastomeric second stage bushing about the second stage shaft; and an axle housing about the second stage bushing, the first stage shaft, the first stage bushing, the second stage shaft and the second stage bushing being collinear and coaxial.
In one embodiment of the present invention, two multi-stage torsion axles are used with one connecting arm attached to both multi-stage torsion axles and a wheel rotatably attached to the connecting arm, the axis of the wheel being 90xc2x0 to the axis of the multi-stage torsion axles. In an alternate embodiment of the present invention, two multi-stage torsion axles are used with a connecting arm attached to each multi-stage torsion axle, each connecting arm having a wheel rotatably attached to the connecting arm.
In a preferred embodiment of the present invention, this is accomplished by providing a multi-stage torsion axle comprising: a rectangular first stage shaft; a plurality of circumferentially spaced apart first stage elastomeric members positioned about the first stage shaft; a hollow rectangular second stage shaft, the first stage shaft and the first stage elastomeric members being positioned therein, corners of the first stage shaft being offset 45xc2x0 from the corners of the second stage shaft; a plurality of circumferentially spaced apart second stage elastomeric members positioned about the second stage shaft, resilience of the first stage elastomeric members being less than resilience of the second stage elastomeric members; a rectangular tubular axle housing about the second stage elastomeric members, corners of the second stage shaft being offset 45xc2x0 from corners of the axle housing; and a stop mechanism directly transferring torque between the first stage shaft and the second stage shaft, when the first stage shaft has rotated more than a predetermined amount relative to the second stage shaft, the first stage shaft, the first stage elastomeric members, the second stage shaft and the second stage elastomeric members being collinear and coaxial.
In a second embodiment of the present invention, this is provided by a multi-stage torsion axle comprising: a resilient first stage torsion apparatus having a first stage shaft; a resilient second stage torsion apparatus surrounding the first stage torsion apparatus, the second stage torsion apparatus having a second stage shaft; and a stop mechanism directly transferring torque between the first stage shaft and the second stage shaft, when the first stage shaft has rotated more than a predetermined amount relative to the second stage shaft.
The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing figures.